1. Field of the Invention
The present invention relates to image observation apparatus for projecting image information directly onto the retina of an observing eye to permit observation thereof and an image observation system using the apparatus, and to image observation apparatus for causing a plurality of parallax images to be incident on a single eye to permit an observer to observe a three-dimensional image in a natural state without causing fatigue of the observer's eye and an image observation system using the apparatus, which are particularly suitable for three-dimensional display and three-dimensional observation in a wide angle of view.
2. Related Background Art
The image observation apparatus of the type for directly projecting an image onto the retina has been known heretofore as apparatus for permitting observation of image information based on image display means such as a liquid crystal display panel or the like. For example, the method disclosed in Japanese Patent Publication No. 2679176 permits the observation of image information in similar fashion to the principle of pinhole camera, by illuminating a display element by a point light source and focusing an image of the point light source on the entrance pupil of the observer. This construction allows the observer to observe clear image information, independent of the imaging performance of eye.
For observation of a stereoscopic image, a pair of image observation devices are provided for the left and right eyes to effect stereoscopic vision by use of binocular parallax. In this construction, focusing conditions of observed images are independent of the accommodation of the eyes. Therefore, this construction can reduce contradiction between convergence and accommodation of the observing eyes in observation of the stereoscopic image by use of only the binocular parallax, so that the observer can observe the stereoscopic image well in the natural state.
The image observation apparatus of the type for directly projecting the image onto the retina is not suitable for observation of image information in a wide angle of view, because the size of an incident beam is fundamentally small at the position of the entrance pupil of the observing eye. This is because, as illustrated in FIGS. 38A and 38B, when the eyeball E is rotated around the rotational center C of eyeball so as to gaze at the marginal part of the field, a difference is made in the relation between the rotational center C of eyeball and the position of the pupil P (entrance pupil) and the beam is intercepted by the iris I because of change of the position of the pupil P to fail to enter the eyeball, thus disabling observation.
FIG. 38A shows a situation in which the eye is gazing at the center of the field of image information, wherein display rays 200 travel through the pupil P without being intercepted by the iris I, to enter the observing eye E. However, when the eyeball E is rotated in order to gaze at the marginal part of the field as illustrated in FIG. 38B, the display rays 200 are intercepted by the iris I to fail to enter the observing eye E. Symbol L indicates the direction of the visual axis.
An object of the present invention is to provide image observation apparatus capable of guiding rays into the eyeball without interception at the iris even in the eyeball state rotated from the center of the field to gaze at the marginal part of the field during observation of the image information displayed on image display means, thus implementing display and observation in a wide angle of view, and capable of reproducing a space in a wide range in the depth direction during observation of a stereoscopic image, and also provide an image observation system using the apparatus.
On the other hand, various proposals have been made heretofore on methods of reproducing the stereoscopic image. Popular methods among these are methods of realizing observer's stereoscopic vision by use of binocular parallax (polarizing spectacles methods, lenticular methods, and so on). In addition, in order to avoid the contradiction between accommodation and convergence of eyes, some attempts have been made to develop methods of reproduction of three-dimensional image satisfying the other stereoscopic recognition function of eye, without relying on only the binocular parallax.
According to Chapter 3, Paragraph 8 “Studies about stereoscopic vision of super-multiview regions” in the publication “Final outcome reports of advanced stereoscopic motion picture communication project” issued in 1997 by Telecommunications Advancement Organization of Japan, it is reported that, under stereoscopic display of “super-multiview regions” in which the view point is sampled at a frequency higher than the spatial frequency of the pupil and in which continuous parallax is reproduced as in the case of an actually existing object, a plurality of parallax images are incident to a single eye of an observer and this presents the effect of guiding the accommodation of focus of the observer's eye to near a pseudo stereoscopic image induced by the binocular parallax, thereby reducing fatigue and dysphoria of the observer. Namely, the publication describes the remark that stereoscopic display with less fatigue of eye is achieved by the “monocular parallax effect” when the conventional stereoscopic display method of presenting parallax images from two view points to the two eyes is extended to a method of presenting parallax images from n view points to n view points and when the distance between two adjacent points of the n view points is set smaller than the observer's pupil.
However, for implementing the stereoscopic display of the “super-multiview regions,” it is necessary to present extremely small parallax images to the observer and it thus becomes necessary to handle very huge volumes of image information. In addition, an extremely quick information display means is necessary, because all the parallax images need to be displayed within the permissible time for persistence of vision of the observer's eye.
In Japanese Patent Application No. 2000-28853 filed by Assignee of the present application, we proposed the image observation apparatus capable of implementing the stereoscopic display of “super-multiview regions” without use of very quick image display means and image generating means nor many image display means. This method is characterized in that an exit pupil of a display optical system is optically divided into a plurality of regions, parallax images corresponding to the respective regions are guided to each observer's eye to cause the parallax images to be incident on the single eye, and image observation devices are provided respectively for the left and right eyes, thereby reducing the number of parallax images to be displayed on each image observation device.
For constructing the image observation apparatus capable of displaying the stereoscopic image in a wide angle of view, it is necessary to set the size of the exit pupil of the display optical system to a large value in order to adapt for movement of the position of the pupil (entrance pupil) with motion of the visual axis for the observer to gaze at the marginal part of the observation field. For example, when the display view angle in the horizontal direction is 2θ as illustrated in FIG. 37, the minimum horizontal width necessary for the exit pupil of the display optical system is given by 2×L×sin θ. Here L indicates the distance between the eyeball rotation center 01 and the entrance pupil P of the observing eye and is about 10 mm. For example, when 2θ=30°, the horizontal width of the exit pupil is 5.2 mm. When 2θ=50°, the horizontal width is 8.5 mm. In practice, values of about 8 mm and 12 mm are adopted in the cases of 2θ=30° and 2θ=50°, respectively, including some margins for the above-stated values in consideration of sizes of pupils, deviation upon mounting, and so on.
For making a plurality of parallax images incident on a single eye, spacings between centers of the respective regions obtained by dividing the area of the exit pupil into plural regions need to be smaller than the size of the observer's pupil; specifically, about 2 mm, for example, Namely, the size of each region has to be not more than a predetermined size, irrespective of the display view angle.
For the above reasons, many parallax images have to be generated and displayed in order to provide the image observation apparatus permitting the observation of the stereoscopic image in a wide angle of view, and it thus becomes necessary to use very quick image display means and image generating means and many image display means.
Another object of the present invention is thus to provide image observation apparatus being capable of implementing the stereoscopic display of the super-multiview regions in a wide angle of view and thus permitting the observer to observe the stereoscopic image well without fatigue nor dysphoria, and to provide an image observation system using the apparatus.